(1) Field of the Invention
The present invention belongs to the field of arrangements for moving a rear door of an aircraft, particularly for rear doors that open inwardly, that is, toward the interior of the fuselage.
(2) Description of Related Art
Rear doors for aircrafts, and especially for rotorcrafts, are advantageous in that the general operability and accessibility are better than when the loading takes place through a side door. Rear doors which, moreover, are able to open inwardly present some additional benefits when compared, for instance, to clamshell doors that open outwardly in a swinging manner—for example, they are not an obstacle for sliding doors attached to the side of the fuselage or for moving and working around the aircraft, which is of the utmost importance when operators intend to load a person into the aircraft in a terrain with space constrictions, such as in rocky mountainous areas.
Besides, rear doors opening inwardly are not affected by the rotor downwash if the rotor is in operation when the doors are open—in clamshell doors, the holding means, such as hinges, mounts and dampers, must be designed to withstand the downwash of the rotor, and the operator opening the door needs more force to push against the downwash. The ambient temperature variations inherent to the different performances of the rotorcraft lead to a significant decrease of the holding means properties, due to the heating and cooling of the internal oil. Moreover, dirty working conditions cause an increased abrasion of the holding means' sealing. All of this makes it difficult to optimize the design of clamshell doors' holding means capable of bearing the downwash.
Furthermore, the aircraft's rear part is a critical design element for the reduction of aerodynamic drag—in order to achieve so, the silhouette of the rear part is often streamlined, which leads to a design commonly referred to, in aircrafts, as fishtail. However, in rotorcrafts, the rear loading accessibility is limited when the rear part, including the tailboom, is streamlined—it is therefore difficult to reach a compromise between a good accessibility and acceptable drag values. As a result from this, rear clamshell doors for aircrafts are normally heavy and not easy to operate with. Contrarily, rear doors which open inwardly have a good aerodynamic performance without limiting the rear loading capability.
Some prior art documents propose alternatives to clamshell doors based on rear doors which open outwardly with respect to the fuselage.
The patent EP 1881928 B1 describes a single rear door sliding outwardly up to the lower region of the tailboom. This solution requires robust and heavy attachments and, when in an open position, the door is affected by the rotorwash. Besides, the open door reduces the space under the tailboom.
The U.S. Pat. No. 3,147,942 discloses a closure and loading device for closing an opening in a cargo carrying compartment and for functioning at the same time as a cargo loading and unloading means when it opens outwardly.
The U.S. Pat. No. 5,241,722 describes a ramp system for cargo aircrafts divided in a fore and an aft ramp, the fore section being capable of moving in the pitch direction relative to the aircraft.
Rear doors capable of being housed at the interior of the fuselage are also known in the art.
The U.S. Pat. No. 8,141,821 B1 discloses a rear door having an upper and a lower wall, wherein the lower wall opens outwardly in a sliding manner up to a position in which it is adjacent to the lower part of the fuselage, and the upper wall opens inwardly by means of an arrangement consisting of a variable-length actuator and of an axis, located on the upper edge of an opening, around which the upper wall rotates guided by the telescopic extension of the actuator.
Likewise, the U.S. Pat. No. 4,097,009 describes another rear door with two walls, the upper one opening inwardly and the lower one opening towards the exterior of the aircraft. The arrangement operating the lower wall is capable of locking such wall at a certain position in which this wall plays the role of a ramp cargo door; the arrangement for the upper door comprises an actuator, in the form of a piston and a cylinder, and a hinge around which the wall can rotate.
The arrangements for inwardly folding a rear door by rotating the door around a fixed axis or hinge do not provide the versatility of movements necessary to place the folded rear door at a position where there are less space constraints.